Edge flame dynamics and statistical behavior in premixed hydrogen-air combustion under inert and reactive wall conditions

This study explores the dynamics and statistical properties of edge flames during the extinction and re-ignition processes in turbulent premixed combustion under statistically stationary Flame-Wall Interaction (FWI) scenarios. Direct numerical simulations (DNS) are used to investigate the role of edge flames in these processes, comparing the behavior of head-on and entrained edge flames under inert and reactive wall conditions. The results reveal that the head-on edge flame primarily governs the flame extinction process, while the entrained edge flame dominates the re-ignition process. This distinction is attributed to the opposite absolute flame speeds: the head-on edge flame exhibits a negative flame speed, while the entrained edge flame has a positive flame speed due to exposure to fresh reactants. The reactive wall significantly influences the entrained edge flame by absorbing radicals, raising the wall temperature, and reducing the wall heat flux due to the suppression of low-temperature radical recombination. Head-on edge flames align with compressive, unstable focus or unstable node–saddle–saddle topologies, whereas entrained edge flames occupy stretching, unstable focus or triple unstable node regimes. These findings highlight the importance of considering edge flame-wall interaction in modeling flame extinction and re-ignition dynamics.

Novelty and significance

This study presents a novel analysis of edge flame dynamics in premixed flame-wall interaction (FWI) under inert and reactive wall conditions. It emphasizes the significant differences between head-on and entrained edge flames, focusing on flame dynamics, characteristics, kinetics, and local flow topologies. The findings offer valuable insights into the complex interplay between flow structures and flame orientation, particularly in industrial combustion contexts. This work deepens our understanding of edge flame behavior, with potential applications in enhancing flame stabilization and advancing pollutant control strategies in combustion systems.